A pedometer is a wearable device that tracks the steps that a user takes over time. In some instances, the pedometer is attached to a person's belt or another location on the user's body or clothing. As the user takes a step, an accelerometer or pendulum integrated into the pedometer senses the user's movement associated with the step and increments a counter that tracks the number of steps. In addition to pedometers, other types of activity trackers can be worn around a user's wrist. Some of these activity trackers share similarities with the pedometer. For example, these activity trackers can count the movement of the user's arm as well as the movements that are related to the user's steps.
One type of activity tracker is disclosed in U.S. Pat. No. 6,675,041 issued to Elisabeth N. Dickinson. In this reference, an apparatus for tracking net consumption of calories by a user has an input to allow a user to enter the number of calories in food consumed by the user. The apparatus also includes a heart rate monitor and a timer. A processor in the apparatus can calculate the number of calories expended by the user in an exercise session based on the duration of the exercise session, as measured by the timer, and the intensity of the exercise session as measured by the apparatus. The apparatus may be provided as a light weight self-contained wrist wearable instrument. The apparatus simplifies tracking the expenditure of calories in exercise and makes it possible for the user to vary dietary constraints on calorie consumption in accordance with the amount of exercise in which the user has participated. Another type of activity tracker is described in U.S. Pat. No. 6,823,036 issued to Yu-yu Chen.